After looking around online for the Avatar soundtrack (which isn't as good as I had thought it would be) I've found several books already out. From the art of Avatar to a secret field manual for Pandora, there are some options out there for getting to know the world a little better.
I have never really caught onto the whole supplemental material thing with movies but I think this time it's going to be different. I'm going to compile some sources as I find them and will publish here once complete. My week-day life is crazy busy so will probably be next weekend. I would also like to find some references on the Na'vi language. What I got from the movie sounded like a real language that was then customized for the Na'vi.
Yes, I'm still obsessed with Neytiri!